Allow the user to retry a grade fetch/submit errors

Currently, the only way a user can retry fetching a grade is to close the error dialog, navigate to another student and then back. And the only way to retry a submitting a grade is to close the error dialog and click submit again. In some cases these errors may be a configuration issue, but in other cases they may be transient and it may be legitimate to retry the request.

Adding a retry button on these error messages will allow a user to retry each request.


SPIKE: Make sure this feature is valid. That is to say, if retry can in many cases work, then its probably a useful feature, but if in most cases retrying won't change the error, then this is not a very useful feature.